Not sure what happened to the amp.Had it installed in my car,it was working fine then the low ohm green led started to flash on and off and i could hear a thump from rear speakers each time it flashed.Also the red on led would come on only for a split second then the green led.I had the amp hooked up to a factory head unit in a 2002 Neon.I placed a 10k resistor on the positive speaker level wire before hooking to the amp on both left and right channels.I have another setup like this running the front speakers and am having no problems with it.What could be the matter!!!
A 10 k resistor on the speaker hot lead Hummm ?? Not exactly a hi to low converter. Humm.
I would suggest buying a real hi to low converter setup as you don't know if the stock deck was using a bridged output. If so then your ground will also have a signal coming on it
You most likely have blown output transistors in one or possibly both channels. BUT you could also have frontend damage because of your special hook up to the RCA's ?????
You're gonna have to ohm them all out (should not be too many due to the size of your amp, I believe 4 per channel on your 50 watter)
They will be number either 2N6488/2N6490 or BDT81 / BDT 82.
The Philips BDT's are obsolete and rare to find. But you can replace them with the 2N's I listed above. Just replace the entire set with the 2N's .
You can look up the numbers with your browser just list one of the numbers in the search bar and search the WWW for any info you need.
There are two types of transistors NPN and PNP use the replacement NPN's for the original NPN's, and so for the PNP's.
Also look for burnt up resistors and such, maybe post a pic for me or the other guys to see the inside of your amp.
Perry or TO-3 can be of help for you also among others here on DIY
hope this helps
I would suggest buying a real hi to low converter setup as you don't know if the stock deck was using a bridged output. If so then your ground will also have a signal coming on it
You most likely have blown output transistors in one or possibly both channels. BUT you could also have frontend damage because of your special hook up to the RCA's ?????
You're gonna have to ohm them all out (should not be too many due to the size of your amp, I believe 4 per channel on your 50 watter)
They will be number either 2N6488/2N6490 or BDT81 / BDT 82.
The Philips BDT's are obsolete and rare to find. But you can replace them with the 2N's I listed above. Just replace the entire set with the 2N's .
You can look up the numbers with your browser just list one of the numbers in the search bar and search the WWW for any info you need.
There are two types of transistors NPN and PNP use the replacement NPN's for the original NPN's, and so for the PNP's.
Also look for burnt up resistors and such, maybe post a pic for me or the other guys to see the inside of your amp.
Perry or TO-3 can be of help for you also among others here on DIY
hope this helps
Thanks for your speedy reply
The amp has this layout for the transistors...
Bdt82-Bdt82-Bdt81-Bdt81-Bdt82-Bdt82-Bdt81-Bdt81
You mentioned some alternatives,which one replaces Bdt82 and which one replaces Bdt81?
Also...the pcb is not burn't or charred anywhere nor are any resistors.I have to borrow a digital camera to get a picture for you.I wondered if the 2 gang input gain pots have damage.How would I tell?
This has to be one of the best sounding car amps that I have heard,I don't want to lose this one.
M.
The amp has this layout for the transistors...
Bdt82-Bdt82-Bdt81-Bdt81-Bdt82-Bdt82-Bdt81-Bdt81
You mentioned some alternatives,which one replaces Bdt82 and which one replaces Bdt81?
Also...the pcb is not burn't or charred anywhere nor are any resistors.I have to borrow a digital camera to get a picture for you.I wondered if the 2 gang input gain pots have damage.How would I tell?
This has to be one of the best sounding car amps that I have heard,I don't want to lose this one.
M.
Rigs64 said:
You can tell if the Phier pots are bad because they have fall outs when you operated them or they are just plain scratchy as a heck, and unlistenable to put up with.
as for weather its the transistors a simple ohm check will verify that issue or not instructions below.
As for the outputs just ohm them out by placing one pin of you voltohmmeter on the center pin and measure the outer two pins. If they read less tha 100 ohms they are most probably bad.
Typically they will read in the 1 to 10 ohm scale or sometimes less. Oh and remember this,,, The lowest reading transistor is usually burnt, but the one next to it might read fine after you pull the bad one, but its always good measure to install a nice new set of outputs as the seemingly good transistor has been exposed to a very harsh situation and most surely has sustained damage
BDT 81 is a NPN device so is the 2N6488
BDT 82 is a PNP device so is the 2N6490
Replace accordingly to TYPE
If you have not found shorted outputs then look for a shorted power supply diode. This is where a pic comes in handy.
But gereally speaking either outputs or diodes cause the majority of issue like you have described,
If its not those then you just might be in over your head and might consider letting a qualified tech solve the issue and give you a warranty to.. just a thought as it takes time and training to troubleshoot electronics and if you have niether then you must face the situation an ask yourself whats in your best interests.
as always I hope this is found helpful
Thank's alot justonemoreamp.I will test the outputs as you have said to.Pots worked fine before this problem(smooth running,no scratch or fading).I will also check the diodes with the meter.I will post a picture of the amp possibly tomorrow when I get ahold of a camera.I am doing this because it's been a long time since I played around with electronics,spent my time designing and building exotic speaker enclosures.I custom build all my crossovers including winding the air core inductors.Got a nice set of tapered pipe fronts with a dual chamber dual reflex sub for home theatre.Anyway....thank's again for all your help,will get back to ya with the test results when I get done.
M.
M.
Update for justonemoreamp
Update for justonemoreamp....found a bad BDT82 in the left channel.I removed it,briefly put power to the amp and it powered up.I have a full set of new motorola transistors on order,decided to use the 2n6488/2n6491 complimentary pairs that you mentioned.Thank's for all your help/advice in saving this amp(plus saving me a repair bill).I have bought a new Pioneer head unit,the factory head unit resistor rig that I created has been de-commisioned and layed to rest in the garbage.
Mike
Update for justonemoreamp....found a bad BDT82 in the left channel.I removed it,briefly put power to the amp and it powered up.I have a full set of new motorola transistors on order,decided to use the 2n6488/2n6491 complimentary pairs that you mentioned.Thank's for all your help/advice in saving this amp(plus saving me a repair bill).I have bought a new Pioneer head unit,the factory head unit resistor rig that I created has been de-commisioned and layed to rest in the garbage.
Mike
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